Telephone system.



H. G. WEBSTER.

TELEPHONE SYSTEM.

APPLICATION FILED AUG.13, 1906.

2 SHEETS-SHEET 1.

Patented Aug. 24, 1909.

H. G. WEBSTER.

TELEPHONE S YSTEM. APPLICATION FILED AUG.13, 1906.

93 1 ,906. Patented Aug. 24, 1909.

2 SHEETS-SHEET 2.

v step-by-step mechanism preferably actuated UNITED, STATES PATET, union.

HARRY G. WEBSTER, OF CHICAGO, IL LINOI S, ASSIGNOB TO MILO KELLOGG, OF CHICAGO, ILLINOIS.

iiELE PHONE SYSTEM.

Specification of Letters Patent.

Application filed August 13, 1906.

Patented Aug. 2st, 1909. Serial No. 330,403.

-ab.ly associated with-the subscribers lines,

mechanism "being provided for each subscribers line which is automatically actuated when, the receiver is taken for use to connect the subscribers'line to an idle linlo circuit and :to cause the display of a calling signal associated with a manually controlled terminal ofthe link-circuit. In systems of v this character, the automatic mechanism has heretofore been controlled by relay magnets in a strictly local circuit, the circuits of these magnets being initially controlled by a relay normally included in circuit with the line limbs.

One object of the' present inventzon is to provide means 'whereby the last mentioned relay may be dispensed with and the line be normally connected to the local circm't, in an organization in which electrical variations occurring in the local circuit shall not be unduly propagated upon either of the line limbs. i r i A further object of my invention is the pro vision of novel means for indicating the presence of an accidental ground upon the outside circuit of the line and improved consists in the novel structure of the relay magnet which responds at one time to current in the line, and subsequently is energized by current inthe local circuit. In accordance with my invention 1: provide for each 'subscribers line a traveling switch which is preferably a rotating switch adapted to carry its movable contacts in one direction only. This switch is rotated by by current from a pulsating generator.

,The switch is provided with three moving contacts or wipers which consti- "=*tute the terminals individual to the line,

1 engaged there by which constitute terminals of thecircuits individual to various linkoonductors. These -link-conductors terminate preferably in cords and plugs at the various operators positions of a multiple switchboard, and the subscribers lines are provided with multiple jacks at the multiple sections. The wipers of the traveling switch have a normal position in which they do not engage any of the fixed contacts of the switch, and when rotated will engage preferably first the contacts connected to a linkcircuit terminating at the first operators position, then contactsconneeted with a linkcircuit at the second operators position, then and so on; and these fixed contacts are multiply connected to similar switches individual to other subscribers lines in a group. The other link-circuits terminating at the first,.second; third and other operators positions may be similarly connected to the switches of lines in other similar groups. The arrangement is such that if the linkconductor connectedto the first terminals of switch will step ahead to the second terminal when it will come to rest and the operation of associatedmechanism will connect the line limbs to the talking conductors of the link-circuit and cause the display-of a calling signal associated therewith@ The operator, after ascertaining What connection is desired, tests the multiple jack of the desired of the plug and rings the subscriberin the usual way. \Vhen conversation is finished, the removalor" the connecting plug causes a further wipers to their normal position.

become accidentally crossed or grounded, the switch will rotatewithout stopping; or will stead of coming to rest and indicating a call, will be caused to continue'it's rotation thereselecting an idle circuit, and the continuous rotation of the switch will therefore inclicate to those in charge the presence of the accidental cross or ground.

To secure the proper operation of the apparatus and circuits, I provide three. relays individual to the subscribers line and'in this one leading to the third operatofisposition i a particular group of switches be in use, the

and so on until an idle link-circuit is reached rotation of the switch to restore its after indefinitely and without subsequently respect the present invention differs from.

line and makes connection by the insertion The organiZation is such that if the line be stepped to an idle link-circuit, but innection of the link-circuit. The third relay which may be called a release relay is energized at the removal of the connecting plug from the jack of a called line, and controls a circuit which causes the switch to return to normal or to rotate continuously.

In further accordance with my invention I associate with that end of the link-circuit leading-to the fixed contacts a pair of relays which serve to control the display of the calling signal and to control the circuit of the private and release relays; and so connect them that although connection is first completed for one talking wire only ofthe link-circuit, when the switch comes to rest, the relay, which is associated with, that talking wire and which serves at that instant to control the circuit of the release relay, shall not be operated before the other relay associated with the opposite talking wire of the link-circuit can operate.

My invention will be more fully understood from the accompanying drawings in which-- a Figure 1 illustrates two subscribers lines extending to a central oflice and there associated with an appropriate link circuit, the

entire organization being in accordance with a preferred form of my invention. Figu 2 illustrates a modification of the line circuit arrangement of Fig. 1, Figs. 3 and 3 illustrate a novel form of relay adapted for use as the private relay in the structures of Figs. 1 and 2, and Fig. 4 illustrates a further modification of the line circuit of Fig. 1.

Like characters refer to corresponding parts in the several figures.

Referring to Fig. 1, two subscribers lines A and B are shown, the substations, being provided with the usual bell and condenser in permanent bridge of the line and the receiver a" and transmitter tbeing in the nor.- mally open bridge closed at the upper contact of the hookswitch'h. The limbs 1 and 2 extend to the central ofiice and are there connected to the central battery G through the normally closed'contacts of the cut-oil relay 3 and through winding 22 .of the private relay 4. A rotary switch is provided for each line which is diagrammatically indicated as having a ratchet wheel 6 and wipers a, b and 0 carried on a shaft 38, the same being driven with 'a step-by-step motion by the motor magnet 7 when 'included in a closed circuit with the pulsating generator G. The wipers a and b are associated with limbs 2 and l of the line respec tively, and when the shaft is'rotated by the action of the magnet 7, they engage the contact piecesor fixed contacts a, a and b, b,

respectively, moving'out of engagement with one contact piece before engaging the next. l/Vlper 0 is shown as having a broad terminal and is associated with the local circuits of as shown, to the wires of a link-circuit terminating at what may be assumed to be a second operators position, and so on through all of the contacts of the switch. The wires leading from the fixed contacts are indicated as being carried through a distributing rack 78, by which any other deired distribution or association of the fixed "contacts and linkconductors may be made throughout the exchange. The switch is also provided with so-called off-normal contacts numbered 8, 9, 10, 11 and 83, which are normally in the position shown; but which are actuated at the first step of the switch to separate contacts '8 and 83, to cause contacts 9 and 10 to engage and 10 and 11 to immediately thereafter disengage. A release relay 5 is provided which is-energized at the time of release and thereafter remains energized until the switch comes to rest.

lVhen a subscriber desires to initiate a call, the removal of his receiver closes a circuit which may be traced as follows: from the upper terminal of. battery C through winding 22 of relay 4, contact 29 and armature v 32 of relay 3, limbs'l and 2 of the line, armature 34 and contact 35 and through contacts 83 and 8 to the ground or return side of the battery.- This current energizes relay 4 and operates all of its contacts. 1

of armature 26 disconnects wiper Z) from its connection with the cut-off relay, and con- The attraction 5 nects the test terminal 37 of the spring-j ackj to battery C through winding 2 and resistance 23 of relay 4, thus prgfi iding the necessary potential at contact 37 of-the jack to indicate that the line is busy at this time.

The attraction of armature 20 disconnects the winding of relay 3 from the return side of the battery, thus preventing the energization of the relay by the battery connect-ion just described, and completes the circuit of generator G through motor magnet 7.- The attraction of armature 15 disconnects the private wiper c from its normal earth connection at contact 16 and connects it to the normally closed contact 13 of the release relay 5. As Wlll'bB pointed out hereafter, the contacts engaged by. theprivate wiper are connected to earth when their correspondin link-conductor is in use, and if it be idle, the wire leading from this contact stands open; and it will be assumed for the purpose of thi$ description that the link-circuit corresponding to c is at this time busy. At the energization of magnet 7-, the switch makes one step, and the following action takes place. The separation of contacts 83 and 8 remove'the normal ground from limb I 2; the engagement of contacts 910 connects the Winding of the release relay to ground, and the disengagement of contacts 10 andll interrupts the connection between the windlngof relay 5 and its contact 14 for a purposeto be subsequently explained. The engagement of Wiper c with contact 0, which is now, assumed to be connected to ground or r the return side otthe battery, completes an,

energizing circuit for relay 4 which may be traced from the upper terminal of the batter through the Winding 21 of relay 4, the conhacts 14-13 of relay 5, contact and armature 15 of relay 4, and thence through wire 87 to the wiper c, and'to groundthrough the wire leading'from contact 0. This c1rcuitserves to maintain the energization of relay 4 and thus the circuit of motor magnet 7, and the switch takes another step.- It is to be noted-that during. the stepping of the wipers, wiper a is disconnected from the line limb 2 atlcontact 33, and wiper b from the other side ofthe line circuit at contact 25. As wiper cLduring the second step moves off. contact a and on to contact 0?, which is open at this time atlcontact 49, and. at switch-99 oi the link-circuit, the energizing circuit just traced through winding 21- is inter- 1'upted, and the energizing circuit previously traced, through winding 22 and through the-. line limbs was interrupted at contact 83 atthefirststep of the switch. Relay 4 is therefore-idenergized and its contacts assume their normal position. The retraction of armature 20 opens the circuit of magnet 7,. preventing further rotation of the switch,

'and'connectsthe winding of relay to the returnssideofthe battery. -,The retraction. of

armature 15 connects wiper c [to ground through contact lmar nature 31 and contact 27., .tneobject of. this ground connection at thisuustant beingto create the busy condition-immediately upon, all contactsflc of other switches-in the group.- The retraction of: armature 26 connects' wiper'b' to the windiug of the. cut-off relay and to contact 30 of limb 1 through wire 86 and contact 25. vWiper Z) being now at rest upon contact ZF, a

circuit for relay 3 maybe traced from the upper'terminal ofthebattery through relay 60, Wire 40 of he lihiccircuit, contact Z)", wiper b, wireiSG-L contact 25, armature 26, the winding of relay-3 and to the return side of the battery throughcontact 18 and armature 2(i..and contact 25 to the. circuit Wire 40, at armature 57 and contact 58.

b, wire 86, contact 25, armature 26, contact 30, armature 32, limbs 1 and 2, armature 34, contact 33, wire 85, wiper a, contact a wire 39, and through the winding of relay 45 to ground, energizing relays 5b and 45. The attraction of armature 53 of relay 45 completes a circuit from battery 0 through lamp 55, armature. 53, contact- 51, and through contact 68 and armature 72 of relay 62 to attraction of armature 47 disconnects Wife 59 from its normal active battery connection at 48, and connects it to the return side of the battery atcoittact 46. The attraction 71, armature 49, contact 50, key 42'a11d wire ground connection to that first established through contact 27, and preventing the wiper c of another sWitch from stopping on a corresponding contact 0 operaton answers in the usual way and, as-

line Byrnakes the usual busy test. If subscriber Bis at this time making a call or-if a connection exists at some other spring-jack or the line, or if'his private-relay 4 be energized as in releasing or when the switch is the potential of contact constantly rotating, 37 willbe raiseda ove that of the earth and the tip of the a current will flow through plug, strand 43, armature 66 of relay 62, contact 65, and to ground through the common test relay 7 The energization of this relay connects windirg T6 of the operators inducarmature 20. Relay 3 being thus energized.

the sleeve 37 of thespring-j'acksand through I i I .previously-; traced, through wire v4O of the link oircuit. The energization of relay '60 has at the-same time connectedrelay 56 to Current will now flow from battery C 3 through relay- 56, wire 40,contact U, wiper the returnlside of the battery, thus display. ing the calling signal to the operator. The

ofarmature 49 of relay 56 subsequently con-\ nectswire 59 through contact 70, armature 11o 4 tocontactc thus providing-analternate Upon observing the calling signal, the

suming that connection is desired with'the tion coil z'to battery, thus giving the necessary testing indication. Assuming the hne to be idle, the operator inserts the calling plug P, when current will flow from battery U, through relay 62, strand 44, contact 37, relay 3, contact 18, and armature to the return side of the battery, energizing both relays. The attraction of armature 72 interrupts the circuit of lamp 55 at contact 68 and completes a circuit for lamp 79 through armature 82, contact 81 of relay 80 and through contact 63 of relay 62, and this lamp 79 remains lighted 'until the called subscriber answers. The attraction of armature 71 of relay 62 interrupts the earth connection of contact c' which was previously established through contact 46 and armature 47 and provides a new earth connection beyond the control of relay 45, at contact 69. The attraction of armature 66 disconnects strand 43 from test relay 75 at contact 65 and completes the circuit of the strand to relay 80 at contact'64. The energization of relay 3 has meanwhile caused the disconnection of limbs 1- and 2 from winding 22 of relay 4 and from the normal earth connection at contact 8, and connected them to terminals 37 and 36 of the jack j at contacts and 33 respectively.

When the ringing key is is operated, current will flow from the generator G through the cord strands and line limbs and to ground or the return side of the generator through resistance 77, relays 3 and 62 remaining enline limbs andto the return side of the bat tcry through relay 80, which by the attraction of its armature 82 extinguishes lamp 79. The two subscribers are now connected for conversation, and current flowing to wire 40, through relays 56 and-60, creates the necessary potential at contact 37 associated with line A to indicate that that line is busy and a similar condition exists at contact 37 of line B. When subscriberA replaces his receiver, the consequent interruption of the 1 circuit through limb 2 deenergizes relay and the retraction'of its armature does nothing but to cause the illumination of lamp 55. When subscriber B replaces his receiver, the consequent deenergization of relay 80 causes lamp v7!);to be illuminated. The illumination of both lamps constitutes thesignal for disconnection, the calling plug P isthen removed and the contacts of relay 3 of line B assume their normal position' leaving the linein readiness for another call. The removal of plug P from the spring-jack likeretraction of its armature 72 extinguishes lamps 7 9 and 55 and the retraction of armature-71 removes, the earth connection from the private contact a andestablishes a releasing circuit :for the switch as follows:

ergized. When the subscriber answers, cur-- rent will flow through relay 62 through the.

wise interruptsthe circuit of relay 62. The

from the upper terminal of battery C through resistance 54, contact 48, armature 47, contact 70, armature 71, armature 50, contact 49, the upper contact of key 42, wire 41, contact 0 wiper 0, wire 87, armature l5, contact 16, armature 31, contact 28, and to the return side of the batter through relay 5 and contacts 109 of the 0 '-normal switch. The ensuing energization of relay 5 causes its armature 12 to engage contact 14, thus completing a circuit from battery C through winding 21 of relay 4 and to ground through the winding of relay 5, and this circuit is thereafter maintained until interrupted at contacts 10- 9 when the switch reaches its normal position. The energization of relay 4 interrupts the circuit of relay 3 at armature 26 and contact 25, which previously existed,through wiper b and relays' 56 and 60, thus allowing these relays to assume their normal-positions. The busy potential is established as before for contact 37, the attraction of armature 15 disconnects wiper c from the contacts of relay 3, thus preventing interference with other connections while the wiper is rotating, and the attraction of armature 20 again closes the circuit through the motor magnet 7. The switch therefore continues to rotate until the normal position is reached, when the interruption of the circuit through winding 21 brings it to rest.

While I have shown contacts on the switch S for but 11 link-circuits, it'is evident that the numberis only limited by mechanical considerations and provision may be readily made for or 100 such circuits. It has been found that when the wiper c is passing over the contacts of busy link-circuits and also when it comes to rest, that momentary variations in-the strength of current flowing through wire 87 at such times are liable to occur, particularly after the surfaces of the contacts and wiper become worn through use. It is evident, therefore, that if but one winding be provided for the relay 4, such, current variations would result in transmitting momentary impulses over the line limbs and that these impulses might create noise in other lines of the system as well as in the receiver of the calling line. To overcomethis objectionable feature, the relay 4 is therefore provided with two windings, 21 and 22, andthese windings are preferably arranged upon opposite ends of the core. The current variations referred to are not sufficient to interfere with the operation of the switch or to allow relay 4 to become denergized and are therefore of instantaneous duration only, and the arrangement of winding shown tends to prevent the propagation of impulsesthrough the line limbs. It has also been shown that when the wiper 0 is moving over busy contacts during the selec; tion of an idle circuit, limb 2 of the line is line limbs, the non-inductive resistance 23 provided'in shunt of winding22 ofthe relay to form a short. circuiting path for any inipulses which may be generated in the winding at this time; and theQarrangement of windings shown constitutes'one feature of my invention. In case limb l of the'line should become accidentally grounded, it will be seen that a circuit is provided for energizing relay 4 through such ground. The attraction of armature 20, completing the circuit of magnet 7 therefore causes the switch to rotate and its rotation will be continued as long as the accidental ground is present and no circuit will be selected. The arrangement of windings indicated also takes care of this condition in which the passing of wiperc from an idle to a busy contact or vice versa will cause an intermittent current fiow through winding 21. It will also be seen from tlie foregoing description that as Wiper c is traveling over busy contacts, the current which then flows through Winding 21 of relay ettends to energize relay' 5 of the 'lineassociated with such busy contacts :jand such busy connection would be released except for the low resistance earth connection existing upon wire 41 of such busy contacts, which is provided at armature Tl and contact '69 I and contact 46. If limb 2 of the line heyet replaced his switch, gagein'ent' with em come accidentally grounded, no operation will'result until the'subs criber tries to make a call. In such case, the operation ,of the mechanism will proceed to the point where circuit is closed throughrelay 56'and relay i5. On account of the presence of the-accidental .ground, relay 45 will be short circuited under these circumstances, and therefore unenergized. The resulting condition will be that as soon'as relay 56 attracts its armature, the releasing circuit is completed from battery (1 through resistance 54, contact -l8, armature 47. contact 70, armature 49,

contact 50,key 2,and thence through wire 41, eperating the. release magnet 5; the sw'itci will then rotate as" at the time of switchreaches normal, the following action will. occ l 11-,

i I I I 1 1 the normal pointasreached is traced from can t H, arm e '12, the winding ofQr-f v lay dj totl] turn side of the bat'tery' through contacts 110-9 of the off-normal As contact ll is brought into entact 10 by the action of IS short circuited through after the circuit of relay 4: through Winding the normal or at armature 47 The releasing circuit ,at the time battery- 1,"; thro gh winding 21 0f relay 4,

contacts 10- 11, contact 14 and arinatin'e'lf2. Immediately there 21 is broken by the separation of contacts 10-9. If at this tlme the circuit be closed through the substation and the accidental ground of limb 2, the relay 4 is maintained energized by the resulting current through winding 22 and does not'release.

The interval between the pulsations from generator G-which causes the step-by-step motion of the switch is such that,.on account of the short circuit referred to, relay 5 does to rotateas long as circuit is closed at "the substation. If the subscriber replaces his telephone, the switch will come to rest when the interruption of the circuit through winding 21 andthe consequent deenergizat-ionof relay 4. This method of securing the continuous rotation of the switch by short circuiting the release when theswitch is passing the normal point, and thus delaying its deenergization, constitutes one of the features of my invention. If the two limbs of the line become accidentally crossed, the apparatus will-operate as if '95 a subscriber Were cailing. When the operator tries to answer the supposed call and finds that the subscriber is not calling, she will release-the connection by operating key 42.

The depression of this key completes a cir- 10.0

cuit from battery"C' through resistance 73 and the lever of key 42 towire 41, thus energizing relay 5 as before and establishing the release circuit. The switch will now rotate-until the normal point is reached but is now prevented from stopping as before, the only difference being that the circuit through winding 22, which was previously completed through the accidental ground of limb'2, is

now completed over limb 2' through armature 3%, contact 35, contact 83, and contact 8 when the normal point is reached. During the time that .the switch is in the normal position, relay 5 as before does not have time to release and the switch therefore continues to rotate, indicating'that the line is in trou bl,e.- If the. subscriber-should accidentally displace his receiver and then immediately replace it, thus closing'circuit through the l-inewlimbs momentarily, it will be evident from the foregoing description that fthe switch would rotate until an idle link-circuit was selectedand that'then, as in the case of the accidental "ground, the energization of relay 56andthe inert condition of relay 45 would result in the establishment of the re-- lease circuit; The switch is then rotated and comes" to rest at the normal position, In order thatthe number of calls handled bv each operator by means of her plurality of broken at contact '30 9-l0ll, and the switch; will thus continue point is again reached through 85 relay during the instant 90 linli-circuitsmay be regulated according to the ability of the operator, or that certain cords which may become defective may be put out oi. service, the key 99 is provided located at any convenient point.' When this key is closed, the circuit thus completed from the intermediate terminal of battery C through resistance-741 and to wire 41 results in n-iaking the cord circuit associated s with that wire and switch artificially busy.

When wiper u in its travel engages the contact of a link-circuit so connected, it the switch be selecting, the current through winding 21 will flow through resistance 74 and to the upper half of the battery. it, for any reason, as the blowing of a fuse, the wiper 0 should come 'to rest on a contact so connected, current would then iiow from the lower half of the battery through resist with the wiper a so that when the private relay is released at the instant of selection, circuit is immediately closed through the relay 115 over the line limbs, and through relay 56 over the winding of the cut-off relay 3; thus allowing wire 59 to be disconnected from the active terminal of the central battery, before it is connected to wire 41 through the operation of relay 56; and consequently preventing the establishment of the release circuit at this time. In the structure of this figure, two windings 88 and 90 are provided for relay et in normal connection with the line limbs, in place of the winding 22 in the former figure. They are difi'erentially connected in order that when the relay is deenergized at the instant of selection, the immediate completion of the circuit through thetwo windings and the line limbs to relay 45 of thelink-circuitshall not cause the relay to become again energized. The difierential connection also prevents current changes in the local circuit including winding 89, which corresponds to winding 21 of the previous figure, from causing inductive disturbances in the substation receiver. The windings 88 and 90 are preferably wound upon a difierent section of the core from that of Winding 89. It will be understood that those portions of the system notshown in this figure may be the same as indicated in Fig. 1. WVhen' the subscriber desires to initiate a call, the closing of the circuit at the substation causes current to flow through winding 88 and wiper a, and then referring to Fig. 1, through v contact a, strand 89 and relay 45 to ground. At the same time circuit 1s closed through relay 56 of Fig. 1, wire 40, contact If, wiper, I

b of Fig. 2, contact25, armature 26 relay 3, contact 18 and armature 20 to ground, The

at this instant being opposed in the two windings, relay *1 remains deenergized and relays 5t; and 45 being energized at substan-- Hall the same instant, the active battery current flowing through windings 88 and 9 0;

connection of wire 59 is removed beforewire,-

59 is connected to wire 1 .1 at contact .The

energization of relay 3-by current through relay 56 then disconnectswinding 88 from limb 1 and short circuitswinding 90 at armature 3. and contact 33, thus cstablishinga satisfactory talking circuit tothe wipers (1 aud o.

position. As in the previous case, the wipers the line while the switch isrotating. The

conditions resultingv from accidental crosses or grounds produce the, same results as in the previous structure.

Fig. 3 adapted for use as the relay 1 in the struc- After the subscribers: ha ve, finished their conversation, the release circuit isestablished in the manner previously described.

and the switch comes to rest at the normal.

illustrates a new form of relay lures of Figs. 1 and 2, the arrangement of springs andwindings being that diagram- -niatically indicated in Fig. 2. The relay has two cores, d and (1, core at being pro vidcd with windings 88 and 90, and core cl with a winding 89.. Apolar extension 6 of magnetic material is provided for the two cores and carries,.on its extremity, the armature f. This armature rocks upon the end of the extension 0, is held in place by the threadedpin n and nut h, is provided withg an air-gap spacer or stopm ot'non-magnetic material, and it is in mechanical engagement with the clrcuit changlng springs 26, 91, 20

and 15 by means of the pieces of insulation and g. The springs and contacts of this figure are those shown at the upper end of the relay core in Fig. Fig. 3.indicatcs the springs at the lower end of the relay core in Fig. 2 and these are assumed to be i mountedupon the extension 0 by the side of those shown in Fig. 3,.and in a similar manner. When the relay is energized by current through either of its. windings, the attraction of armature f raises springs 26, 91,

' relay armaturesl '1- As-" wi'peroengages busy est-hoe 20 and 15, causing them to liseng'age their lower contacts and to engage their upper contacts. By reference to the diagram of Fig. 2, it will be 'seen that the relay is initially energized by current through winding 88; that its subsequent energization is maintained by current through wlnding 89; that, when it isldenergized at the instant of selection,- the circuit through winding 89 is broken while the currents through windings 88 and 90 are opposed; and that, at the time of release, it is energized by current through winding 89. The relay has the ad vantage over those heretofore used in that, when its armature is attracted, current variations inthe windings on one core are not propagated in the windings on-the other core, for the reason that. the magnetic lines of force generated in one core by such variations do not traverse the opposite core on account of the air-gap between such core and the armature, but are shunted therefrom by the closed magnetic path through the extension 6 and the armature. While 1 have shown one particular structural Yarrangement embodyin this principle, I do not wish to be limited to the particular arrangement shown.

Fig. 4 indicates a modification of the line --eircu1t of Fig. l in which the relay is providedwith two windings differentially connected. The energizing Winding 94 is included in circuit with the line limbs and in the local circuit as well; the opposing winding 93 serves to provide a path to earth for.

disturbing currents arising through current variations in the local circuit, thus preventing their undue propagation in the line limbs, without causing such earth. connection to interfere with the operation of relay l. The two windings haveequa-l turns and maybe concentric windings if desired, or may be on different sections ofthe core as shown. The subscriber calls in-the usual way, relay a being energized by" current through winding 94 and when the attraction of armature 95 engaging contact 96 closes a circuit zthrongh-the opposing winding 93,'t he"excess of'icurrent 1n winding 94 is sufiicienttomtiintam the attraction ofthe contacts, the-5 necessary excess of current 1s maintained; an'dflvvhenfwiperc engages the contact of an idle link-circuit, the

interruption of :thisfexcess; current allows.

relay 4' -toibe deenergized';jand the normal 'operation'isin all other-respects similar to that of the structure ot Figi 1. When wiper so is %passing"=oirerbusy contactsduring the process of se'l'ection or constantly rotating through the presence (if-accidental groundsorhrosses o'n the line limbs, the momentary nae-eruption or variation in the-current fi'ow- --ing. tlrrough wire 100 will not cause objeutiombl disturbances uponthe. line l'unbsw for the reason that the disturbing currents, set up in the two windings 93 and-94; atsuch time, will be in opposition'and also for the reason that the earth connection of wire 100, through winding 93,armature 95 and contact 96, tends to prevent an increase of potential at wire 100 when the circuit through wiper c is varied or interrupted.

\Vhile I have described one arrangement of grouping the link-conductors or cordcircuits in their relation to the various switches and to the several operators positions of a system, it is obvious that other methods may be employed, and I do not, therefore, wish to be limited to the particular arrangement described neither do I wish to be limited tothe particular kind'of traveling switch indicated, as it is obvious that various means may be employed for causing the contacts associated with the line totravelover the contacts associated with. the link-.

circuit-s. It will be understood that the va- .rious grounds indicated inthe diagram are connections to thefo'ificereturn or-to the States, is

1 A telephone exchange system-eompris- I ing a plurality of telephone linesya plurality of link-circuits, .a source of current, a traveling switch having movingcontaot's for estab lishing connection between a calling line and an idle link-circuit, driving means for said switch, a controllingma gnet forsaid dIiv-' said magnetoperating when energized to cause the actuation of said contacts, a local control-ling circuit for the magnet, and means for preventing electrical variations in the local circuit from producing disturbing currents in the line.--

2. A telephone'exchainge system comprising a-plu'rality oftelephone lines, a plurality of link-circuits, a source of current, a'traveling switch hav ng 'moving'contacts for establ s'hmg connections between a calllng line and an; idle 'ilinkecircutt, driving means for said switch, a} .controlling magnet for said driving means any: incireuitqwithiihe line, said ma gnetfoperating when energized to cause the actuation of saidomm -a local controlling cir'cil'it for the.inagnet,'=and windings of said magnet sogdisposed-as to 125 prevent electrical "variations in the local 'cir cuitfrom producing disti'zrlo'higv currents in the line.

a 3. :A telephone exchange system-compris ing'a plurality "of telephone lines, a plurality ofli'n-kcircuits, asource ofFour'r-entcaitravelmg means normally in circuit withthe, line,

' ing switch having. moving contacts for'estab lishinlg' nnectionbctween acallingli'ne' and amid e switch, a. controlling magnet for-said driv-- ing means I normally in, 'c'ircu with the line;

sa d "magnet, operating when ener' I cause the actuation of sa d co tacts, 'a' 'locaql' controlling circuit tors-the .jni'agriQt,

isp'osed' as 4.- A telephone exchange js'ystem comprise a-p e l y ofep o .1i e pli l yj of linkrcircuitsa source ofcurrent, a travelingswitch having' moving] contactsfor es tablishing connection between a calling line and an-idle link-circuit, driving means for said switch, a controlling magnet for'said (haying means normally in circuit with the '-l ine,-: said magnet operating when energized to cause the actuation of said contacts, alocal cont1 o1 1ing. circuit for the magnet, and a magnetic; circuit for said magnet so organi'Zed that current variations in the local circuit are prevented-twin producing disturbin'g currents in the line. a

5. A telephone exchange system comprising a plurality of telephone lines,-a plurality of link-circuits, a source of current, a traveling switch having moving contacts for establishing. connection between a calling line and an idle li nkcircuit, driving means for said switch, a controlling magnet for said driving means normally in circuit with the line, said magnet operating when energized tolcause the actuation of said contacts, a localfcontrolling circuit for the magiiet, and

a magneticcircuit and energizing windings for said magnet so organized-that current variations in the local circuit are prevented from producmgdisturbmg currents in the line.

6. A telephone exchange system comprise ing 'a plurality of telephone lines, a plurality of link-circuits, a source of current, a traveling switch having moving contacts for cstablishing connection between. a calling line and an idle link-circuit, driving means for said switcln a controlling magnet for said driving-means operating when energized to cause the actuation of said contacts, an ener gizing winding of said magnet normal-ly circuit with the line, and a neutralizing winding of said magnet momentarily included in circuit with said energizing winding when'said connection is established. 7

v 7. A telephone exchange system comprising a plurality of telephone lines, a plurality of link-circuits, a source of current, a travelingswitch having moving contacts for establishing connection between a calling line andan idle link-circuit,driving means for said switch, a' control ingv magnet for said driving means'operati' g when energized to 'cuit', driving means v-forf said cause the actuation of said contacts, an enercluded in circuit with said energizing winding when" said connection is established whereby current may flow through said ener'-- I 1 gizing lwindin'g without energizing; the

- magnet. i

.. .8; "A telephone exchange system (zomp'ris.

ing a plurality of telephonelines, a plurality of link-circuits, a' source 'otzcurrent, a"travel'-' ing'jswitch having movingv contacts jvfor es- .1

tablishing connection between calling line and an idle link-circuit, driving means r01- fsaid switch, a controllingmagn'et for said.

driving means. operating when energized to cause the actuation of said'conta-cts, anenergizmg winding of said. magnet normally n circuit with the line, an energizing winding;

of said magnet'in a localcircuit, and means for preventing electrical variationsin. the local circuit from producing disturbing currents in the line. I f I u 9.- A telephone exchange system compris- .ing a plurality of telephone lines, a plurality of link-circuits, a source of current, 'a'traveling switch having moving contacts for esiablishir'fg connection between a calling line and anidle link-circuit, driving means for said switch, a controlling magnet for said driving means operating when energized to i cause the actuation of said contacts, an energizing windlug of sald magnet normally in circuit with the line, an energizing winding of said magnet in a local circuit, and a magnetic circuit for said magnet so organized thatcnrrent variations in the local circuitare prevented from producing disturbing currents in the line. I

l0. A telephone exchange system comprising a plurality of telephone lines, a plurality f link-circuits'n source of current, a traveling switch having moviugcontacts for establishi 11g connection between .a calling line and an idle link-circuit, (lriving-nie:-ii1s for said switch. a controlling magnet for said dI'lV-z the actuation of said contacts, an energizing -winding of said magnet normally in circuit with the line, an energizing winding of said, magnet in a local circuit, and a magnetic circuit and energizing-windings for said magnet so organized that current variations in' 'the local circuit are prevented from producing disturbing currents in the line. A

l]. A telephone exchange system (-501H1)1'l5 ing a plurality of-telephone lines, a plurality of linl -circuits, a source of current, a traveling su'itchhavl'ng moving contactsffor establishing connectionbetween a calling line and an idle link-circuit,driving means for said switch, a controlling magnet for said; driving means operating when energizedto causethe mg means operating when energized to cause actuation of said cont-act's, an"-energizing 'iso winding of said magnet normally in circuit with the line, a neutralizing winding of said magnet momentarily included in circuit with said energizing winding when said connection is established, an energizing winding of said magnet in a local circuit and means for preventing electrical variations in the local circuit from producing disturbing currents in the line.

12. A telephone exchange system comprising a plurality of telephone lines, a plurality ot link-circuits, a source of current, a travelin g switch having moving contacts for estab lishing connection between a calling line and an idle link-circuit, driving means for said switch, a controlling magnet for said driving means operating when energized to cause the actuation of said contacts, a release relay operating when energized to establish a locking-circuit for said magnet, means for interrupting said locking circuit when said moving contacts reach their normal position, and means for causing the continuous travel of said switch if said magnet remains energized aftersaid interruption.

1.3. A tele hone exchange system comprising a plurality of telephone lines, a plurality of link-circuits, a source of current, a travel? ing switch having moving'contacts for estab lishing connection between a calling'line and an idle link-circuit, driving means for said switch, a controlling magnet for said driving means operating when energized to cause the actuation of said contacts, a release relay operating when energized to establish a look ing circuit for said magnet, means for interrupting said locking circuit when said movin g contacts reach their normal position, and means controlled by the travel of said switch for reestablishingthe. locking circuit if said magnet remains energized after said interruption.

14. A telephone exchange system comprising a plurality of telephone lines, a plurality of link-circuits, a source of current, a travelin switch having moving contacts for estab lisiing connection between a calling line and an idle link-circuit, driving means for said switch, a controlling magnet for said driving means operating when energized to cause the actuation of said contacts, a release relay operating when energized to establish a looking circuit for said magnet, means for interrupting said locking circuit when said moving contacts reach t eir normal position, and means for retardin the release of said relay at the time of said interruption whereby said locking-circuit may be reestablished by the travel of said switch.

15. A telephone exchange system comprising a plurality of telephone lines, a plurality of link-circuits, a source of current. a travelin switch having moving contacts for establis ling connection between a calling line and an idle link-circuit, driving means for said operating when energized to establish a locking-circuit for said magnet, means for interrupt-mg said locking-clrcuit when said moving contacts reach their normal position, and

means for momentarily short circuiting said relay when said locking-circuit is interrupted whereby said locking-circuit is reestablished if said magnet remains energized.

16. A telephone exchange system comprising a plurality of telephone lines, a plurality of link-circuits, a source of current, a traveling switch having moving contacts for establishing connection between a calling line and an idle link-circuit, driving means for said switch, a controlling magnet for said driving means operating when energized to cause the actuation of said contacts, a release relay in a local circuit operating when energized to establish a locking circuit including a winding of said magnet and said relay, means for interrupting said locking-circuit when said moving contacts reach their normal position, and means for causing the continuous travel of said switch if said magnet remains energized after said interruption.

17. A telephone exchange system comprising a plurality of telephone lines, a plurality of link-circuits, a source of current, a travelingswitch having moving contacts for establishing connection between a calling line and an idle link-circuit, driving means for said switch, a controlling magnet for said driving means operating when energized to cause the actuation of said contacts, a release re lay in a local circuit operating when energized to establish a locking-circuit including a winding of said magnet and said relay, means for interrupting said locking-circuit when said moving contacts reach their normal position, and means controlled by the travel of said switch for reestablishing the locking-circuit if said magnet remains energized after said interruption.

18. A telephone exchange system comprising a plurality of telephone lines, a plurality of link-circuits, a source of current,a traveling switch having moving contacts for establishing connection between a calling line and an idle link-circuit, driving means for said switch, a controlling'magnet for said driving means operating when energized to cause the actuation of said contacts, a release relay in a local circuit operating when energized to es tablish a locking-circiut including a winding of said magnet and said relay, means for interrupting said locking-circuit when said moving contacts reach their normal position, and means for retarding the release of said relay at the time of said interruption whereby said locking-circuit may bereestablished by the travel of said switch.

19. A telephone exchange system compris 20. A telep ing apluralityof telephone lines, a plurality voiE-link-cir'cuits, *a'source of current, a travel mg aplurality of telephone lines, a plurality;

of link-circuits, a source of current, a traveling. switch having moving contacts fr-establ's ing connection between acalling line and 'an idle link-circuit, driving-means for sand switch, acontrolling magnet for said drivingmeansoperating when energized to cause the actuation. of .sald contacts, a releaserela inalocalcircuit operating when energized to establish a locking-circuit including a winding of said magnet and said relay, means for interrupting said locking-circuit when said 'mo'vin contacts reach their IlOI- malgp'osition, an means for momentarily short circuiting said relay when said lock ing-circuit is interrupted whereby said locking-circuit is, reestablished if said magnet remains e'ner zed;

one exchange system comprisinglx's w'itch havin-g'movin'g contacts for establ's ing connection between a calling line and an idle link-circuit, driving means forsaid switch,- a controlling magnet for said driv ing means operating when energizedto cause the actuation of said contacts, anda local controllingcircuitfforlthe magnet in part individual to each link-circuitjand amanually operated connection therefrom to an intermediate terminal {of .said' source to 'prevent the connection of" al line to said lmkcircuit by said switch. j I

-fro1n;fto anintermediate' terminal of said. source" to cause the establishment of ja 're-' lease circuit fora traveling'switch associated with. said,1inkircuit;'

22;; A telephone. exchange system compris' ragaummy oftel'ephone lines,a plurality- .lOCfllj controlling-j circuit for the, magnet in:

6 0;- partfindividnalftoifleach link-circuit and a of lin circuits, ,a; -source o-fcurrent,'a tra v--;

cling; switch having moving contactsfforle'stabh'shing connection between a calling line and anidler ciiicuit,'driving means for idj itgmf a atrolling magnet for said driving means operating when energized to cause theactiiationiof said contacts,- and a mainlally' opsrat'e'd "connection therefrom to an. Intermed ate terminal of said sourceni -hereby throughsaid connection shallat onejjtlme' prevent-the --connection of:

,cator'when a calling line 21. A tele honeexchange' system compris-' a plum ityof telephone-lines, a. plu- 23. A telephone exchange system comprising a plurality of telephone lines, a plurality oflink-circuits, a source of current, a traveling switch having moving contacts for es tabllshing connection between acalling line and an idle link-circuit driving means for said switch, asignal indlcator for, each linkcircuit, a controlling magnet for said driving means normally in circuit with the line,

said magnet operating when energized to 'cause the actuation ofsaid contacts, a local controlling circuit for the magnet, and means for causlnganormal operation of the indilink circuit.

' 24:. A t'elephone exchange system compriscircuit, afcontrollingj magnetffor said driving means operating when energized to cause the actuation of said contacts,a-local controlling-circuit for the magnet, means for causing a normal operationof the indicator when a calling line is connected to'a linkeirc'uit, and means for causing'an abnormal operation of said indicator when a line is abnormallyconnected to a link-circuit -25-. A telephone exchange system comprising a plurality o f telephone lines, a plurality of link-circuits, a source'o'f current, a traveling s'witchhaving moving contacts'for e'stablishing connection between a calling line and an idle link-circuit, driving means for said switc h, a relay 'magnet normally in 'cir-' cuit with the line-for controlling said drivingmeans operatingwhen energized to cause the actuation of said moving contacts,- a cut-j off relay for the line,"arelease relay for the line, an off-normal switch controlled by the motion of the traveling switch, and an energizing'circuit' for the release relay, said circuit. including a' movingcontact ofthe switchand;-.bein controlled at one point by the --fcut-'-o'fl re ay and at another point by con- .-tacts' of' said magnet. v r I 26; A tele hone exchange system'comprising a, plurality of telephone lines, a plurality of link-circuits, a source of current, atraveling switch having moving contacts for establishing connection between a calling line and an idle link-circuit, driving means for said switch, a relay magnet normally in cir cuit' With'the line for controlling said driving means operating when energized to cause f-the actuation of said moving contacts, a but: ofi" relay for'the line, a release relay for the v 0 r I I line, an off-normal switch controlled by the 65; :1; line t'oj fthe l1nk'c1rcu i t' by saidswitch and lmotion of the traveling 'switclnand a local is connected to alease relay and at energizing circuit for said magnet'completed over a movingvcontact of the switch and controlled at one point by contacts of the reanother point by contacts of said ma net.

:27. A to ephoneexchange system comprising a plurality of telephone lines, a plusaid driving-means operating when enerlishing connection gized to cause the actuation of said moving contacts, a cut-oil relayfo'r the line, a release relay for the line, an oil-normal switch controlled by the motion of the traveling switch,and a moving contact for said switch normally connected 'to an inactive terminal of said source, means for including said contact in circuit with an energizing winding of said magnet when energized, means for including said contact in circuit with the release magnet after connection is established, and means for opening the circuit of said 'contact when said magnet and said release relay are both energized. t 28. A telephone exchange system comprising a plurality of telephone lines, a pinrality pf link-circuits, a sourcevof current, a traveling switch having moving contacts for establishing connection between a calling line and an idle link-circuit, driving means for said switch, a relay magnet normally in circuit with the line for controlling said driving means operating when energized to cause the actuation of said moving contacts, a cut-off relay for the line, a release relay for the line, an oft-normal switch controlled the motion or the traveling switch, and a estoring circuit -for said switch completed at the energization of: the release relay, said circuit including 'a winding of said magnet, contacts and windin of the release relay and contacts of the ell-normal switch.

29. A telephone exchange system comprising a plurality of telephone lines, a plurality of link-circuits, a source of current, a traveling switch having moving contacts for estabbetween a calling line and an idle link-circuit, driving means for said switch, a relay magnet normally in circuit with theline for controlling said driving means 0 cratin when ener ized to cause the actuation of said moving contacts, a cut-off relay for the line, a release relay for the line, an oil-normal switch'controlled by the motion of the'traveling switch, a normal battery connection for the cut-off relay controlled at contacts of said magnet, and an energizing circuit for said magnet including contacts of the cut-off relay.

30. A telephone exchange system comprisinga plurality of telephone llncs, a plurality switching means tion between a calling line and an idle linkof link-circuits, a source of current, a traveling switch having moving contacts for establis'hing connection between a calling line and an idle link-circuit, driving means for said switch, a relay magnet normally in circuit with the line for controllingg'said driving through contacts of the cut-off relay, contacts contacts of the off-non of said magnet and mal switch. .o I

31. A plurality of telephone lines, a plurality of associated link-circuits, automatic switching means for establishing connection between a calling line and an idle link-circuit, a relay normally connected to one talking strand of the link-circuit, second relay normally disconnected from the other talking strand of the link-circuit, a controlling circuit for said switching meansjointly controlled by th e relay/sand means for completing circuit through the two relays simultaneously when connection is established between acalling line and the link-cirhcuit.

32. A plurality of telephone lines, a plurality of associated link-circuits automatic for establishing conneccircuit, a relay normally connected to one talking strand of the link-circuit, second relav normally disconnected from the other talking strand of the link-circuit, a controlling circuit for said switching means jointly controlled by the relays, and separate means simultaneously actuated for connecting the link-circuit to a calling line and for connecting said second relay to the said other strand whereby said relays are simultaneously energized.

plurality of telephone lines, a plurality of associated link-circuits, automatic switching means for establishing connection between a calling line and an idle link-circuit, a relay normally connected to one talking strand of the link-circuit, second relay normally disconnected from the other talking strand of the link-circuit, a controlling circuit for said switching means jointly controlled by the relays, an electromagnet for a release relay for the 1 connecting the link-circuit to a calling line,

a second electroma net for connecting said second relay to sai other strand and means for establishing an energizing circuit for the two electromagnets simultaneously, whereby the said relays are simultaneously actuated.

34. A telephone exchange system comprising a plurality associated link-circuit and automatic switching means for connecting said lines for convcrsation, a relay normally connected to one talking strand of thelink-circuit, a

of telephone lines, an

second relay normally disconnected from the other talk ng strand of said link-circuit, a'controlling circuit for said switching means jointly controlled by said relays, and means for com- 7 pleting circuit through the two relays simul-.

taneously when a definite point in the establishment of said conversational circuit is reached.

35. A telephone exchange system coinprising a plurality of telephone lines, an associated link-circuit and automatic switching means for establishing connection between said link-circuit and said lines, a relay normally connected to one talking strand of said link-circuit, a second relay normally disconnected from the other talking strand of said link-circuit, a controlling circuit for said switching means ointly controlled by saidrelays, and separate means simultaneously actuated for connecting the linkcircuit and one of said telephone lines and for connecting said second relay to the said other strand whereby said relays are simultaneously energized.

36. A telephone exchange system comprising a plurality of telephone lines, an associated llnk-circuit and automatic switching means for establishing connection between said link-circuit and said lines, a relay normally connected to one talking strand of the link-circuit, a second relay normally disconnected from the other talking strand of said link-circuit, a controlling circuit for said switching means jointly c0n trolled by said relays, an electromagnet -for connecting the link-circuit to a definite one of said llnes, a second electromagnet for connecting said second relay to said other 

